Preparation And Modification Of Hyperbranched Polyester And Its Application In Unsaturated Polyester Resin

Hyperbranched polymers have many excellent properties such as low-viscosity,high solubility,and high functionality due to their unique molecular structure.They have been researched in resin materials,biomedicine and other fields,and have attracted more and more attention.At present,the study on the preparation of functional materials of hyperbranched polymer and the development of their applications are still hot spots.Unsaturated polyester resin(UPR)with low cost and good processing technology,has developed rapidly in China since it was introduced and taken a certain market share.However,its poor toughness and low strength hinder its further development,so improving the mechanical properties of UPR,enhancing its comprehensive performance is still a significant research direction.In this paper,a low-viscosity hyperbranched unsaturated polyester(HBUP)was prepared and characterized by infrared spectroscopy,nuclear magnetic resonance,gel permeation chromatography and other instruments.And finally it was used to modify UPR via blending.Meanwhile the effects of the type and amount of HBUP on the mechanical properties and thermostability of UPR were also investigated.Firstly,hydroxy-terminated HBP of different generations were synthesized with pentaerythritol as the central monomer and 2-bis(hydroxymethyl)propionic acid as the branched monomer,with the degree of branching between 0.40 and 0.60.And then some of the terminal hydroxyl groups in HBP were grafted by lauric acid to prepare the low-viscosity HBP which is liquid at room temperature.The grafting reaction for third generation HBP was mainly discussed and its optimum reaction temperature is 155 ?,the dosage of catalyst is 0.75 wt%,the reaction time is 3 h.The intrinsic viscosity of HBP in third generation after modification is 4.04 mL·g-1,which is lower than the 5.11 mL·g-1 of HBP in third generation before modification.Secondly,maleic anhydride(MAH)and acrylic acid(AA)were respectively used to modify the remaining hydroxyl groups in low-viscosity HBPs of different generations,thereby two types of low-viscosity HBUPs(MAH-HBUP and AA-HBUP)were synthesized.And they still keep liquid at room temperature.The low-viscosity MAH-HBUP and AA-HBUP from the third-generation HBP have intrinsic viscosities of 4.44 mL·g-1 and 3.72 mL·g-1,respectively,both less than 5.11 mL·g-1 from the third-generation HBP before modification.And both of them also have a wider range of solubility.The maleic anhydride has strong reactivity and its grafting reaction is easy to come true;while acrylic acid has low reactivity,and its preferred conditions for the low-viscosity HBP in third-generation in the research range are:reaction temperature 100?,reaction time 4 h,and the dosage of catalyst 0.80 wt%.Finally,this two different low-viscosity HBUPs based in different generations HBPs were used to modify UPR via blending,respectively.It was found that the low-viscosity MAH-HBUP and AA-HBUP all have the best modification effect when the HBP is in third generation.In the case of low-viscosity MAH-HBUP in third generation,when the amount of it added in the UPR was 4 wt%,the comprehensive performance of the UPR casting body is superior,including the tensile strength of 61.53 MPa,the bending strength of 108.64 MPa,the tensile modulus of 2.30 GPa,the flexural modulus of 2.89 GPa,the elongation at break of 3.8%,and the Barcol hardness of 42 HBa;wherein the tensile strength increased by 20.4%,the elongation at break improved by 90.0%,while the other mechanical properties do not change much.For the low-viscosity AA-HBUP in third generation,when the amount of it added in the UPR was 2 wt%,the overall performance of UPR casting body is optimal,including the tensile strength of 60.00 MPa,the tensile modulus of 2.41 GPa,the bending strength of 108.24 MPa,the flexural modulus of 2.84 GPa?the elongation at break of 3.5%,the Barcol hardness of 40 HBa;and its tensile strength is enhanced by 38.5%,the elongation at break boosted by 84.2%,while other mechanical properties have a small change.The UPR modified by these two HBUPs have a good heat resistance as well.In conclusion,the low-viscosity HBUP was successfully prepared and used to modify UPR by the way of blending in this study.The properties of UPR were well improved with just a small amount of modification by adding HBUP.